In recent years, various technical developments of semiconductor devices that have thin film transistors (TFTs) formed from a semiconductor thin film (in a thickness range of substantially several to several hundreds nanometers) formed on the same substrate are forwarded.
Among such semiconductor devices, a structure in which on a substrate that becomes a panel not only a pixel portion but also a driving circuit as an internal circuit are integrally formed and an external circuit is formed outside of the panel (see Patent Document 1, for embodiment) is known.
On the other hand, when, in order to prepare a system on panel in which an external circuit is integrally formed, the external circuit is tried to mount on the panel, an area for the pixel portion and the driving circuit has to be reduced or a space for mounting the external circuit has to be disposed anew. As a result, there are problems in that not only the high definition and high-speed driving cannot be attained but also a panel becomes larger.